EP0458938B1

EP0458938B1 - Fire fighting system mainly conceived to safeguard forests

Info

Publication number: EP0458938B1
Application number: EP91901284A
Authority: EP
Inventors: Giulio Brogi; Luca Pietranera; Francesco Frau
Original assignee: Selenia Industrie Elettroniche Associate SpA
Current assignee: Leonardo SpA
Priority date: 1989-12-20
Filing date: 1990-12-19
Publication date: 1996-08-28
Anticipated expiration: 2010-12-19
Also published as: BR9007134A; WO1991009390A1; IT8948686A0; ES2094807T3; PT96268A; GR3021588T3; EP0458938A1; DE69028296T2; CA2047190C; ATE142039T1; TNSN90156A1; PT96268B; CA2047190A1; IT1237262B; DE69028296D1

Abstract

Fire fighting system mainly conceived for the safeguard of wooded areas, consisting of a number of peripheral detectors (1) each formed by: an infrared sensor (10), a TV camera (11), a rotating platform (12), a local processor (13), a group of weather sensors (14) and a communications subsystem (15). The peripheral sensors refer to a local control centre, which includes the following: peripheral detector (usually more than one detector is included in each system) (1); communications subsystem (2); central processor (3); software modelling for the forecast of monitored fire development (4); historical data base (5); TV monitor (6); video recorder (7); memory unit (hard disc, tape unit) (8); printer (9).

Description

The invention presented regards an integrated system which is particularly well suited for the safeguard of wooded areas against fires.
In particular the invention refers to a fire fighting system, mainly intend for the safeguard of wooded areas, for raising a fire alarm comprising a peripheral detection station including an infrared sensor for detecting a given surveyed area, which infrared sensor measures the radiation flow coming from a small angular region of said area, rotating means supporting the infrared sensor, which confers an azimuth scan to the infrared sensor, a local processor which acquires data from the infrared sensor and manages data exchange with a local control centre, from which it receives commands, a peripheral station communications subsystem provides for transmission of data to the local control centre; and said local control center including a communications subsystem which receives the data sent by said peripheral station communications subsystem and emits said commands for controlling of the local processor, a peripheral memory unit for recording of data, a central processor which controls the peripheral detection station, controls the exchange of commands and data, illustrates the notified alarm on topographic maps of the area, records data on said peripheral memory unit, displays system status and integrates the notified alarm with data of a historical data bank containing information on the distribution of vegetation of the surveyed area.
At present, the problem of fires in wooded areas has reached worrying levels. The forests of Argentario and Sardinia are sad evidence of this.
G. Jacovitti and R. Cusani describe in the article "A REAL TIME IMAGE PROCESSOR FOR AUTOMATIC BRIGHT SPOT DETECTION", Onzième Colloque sur le Traitement du Signal et des Images, Nice du ler au 5 Juin 1987, pages 587-590, techniques of images processing have been applied to infrared TV images to detect and locate vegetation fires. A peripheral station is equipped with some TV infrared cameras. The cameras can rotate over a 180° angle in the azimuthal plane. The peripheral station is connected via a microwave radio link and a bidirectional UHF radio link to a control station, where the whole surveillance operation takes place.
Thus at least two infrared cameras are required as to scan over 360°. Further in the central control station a very powerful main processor is required as to perform the image processing.
In the described system no weather sensors are provided. The processor can not integrates the received alarm with the current and historical weather data. For that reason there is no possibility to calculate a fire propagation model with information about propagation speed and direction of the fire.
But of course the most frequent inconvenience has always been the late arrival of fire fighters due to the fact that there has never been an instantaneous detection of fire and alarm transmission.
The scope of this invention is therefore a system which offers automatic monitoring of fires and which calculates a fire propagation model. The utilisation of infrared sensors and of all the devices which form the system, are noteworthy step ahead in the safeguard of wooded areas, till present trusted to towers and look out personnel.
Therefore, the fire fighting system is characterised in that the local processor of the peripheral detection station further acquires data from means for collecting current weather data included in the peripheral detection station, provides for extraction of fire alarm and causes the transmission of the alarm signal and the weather data to the local control centre via the communications subsystems, and in that the central processor of the local control centre further integrates the alarm extracted by said peripheral detection station with instantaneous weather data and with data of the historical data bank further containing information on recent weather conditions, as to develop a fire propagation model as a function of said integration, whereby the model is based upon the instantaneous weather data, the vegetation distribution, and the recent weather conditions, resulting in a propagation speed and direction of the fire.
The system of the invention so consists of two sub assemblies: the remote detector and the local control centre. More than one detector can be connected to the local control centre, in quantities from 5 to 10. For illustrative non limiting purposes the invention will now be decribed with reference to the tables of drawings attached.
Figure 1 shows the block diagram of the entire system, where the arrows stand for the connections among the units of the system:

1 Peripheral detector (usually each system includes more than one detector); this block is expanded in figure 2;
2 Communications subsystem;
3 Central processor;
4 Observed fire evolution prediction model;
5 Historical data base;
6 TV monitor;
7 Video recorder;
8 Memory unit (hard disk, tape unit);
9 Printer.

Figure 2 is a schematic representation of the peripheral detector, indicated as block 1 in figure 1. Here we can see:

10 Infrared sensor;
11 TV camera;
12 Rotating platform;
13 Local processor;
14 Weather sensor group;
15 Communications subsystem.

More in detail, the remote detector consists of:
An infrared sensor 10 which has a spectral sensitivity such as to provide an optimum detection of hot sources (300-700 degrees C) against an ambient temperature background (0-40 degrees C). As regards operation and structure of such sensor, refer to the invention filed in Italy on December 21, 1989 with number 48685-A/89 (= WO-A-9109389 & EP-A-458925).
A group of weather sensors 14 which provide data on temperature, relative humidity, pressure, wind speed and direction, solar radiation and rain rate.
A TV camera 11 for possible visual monitoring of the surveilled area. A motor driven platform 12 which confers an azimuth scan to the infrared sensor and to the TV camera over 360 degrees. A processor 13 which acquires data from the infrared sensor and provides for extraction of possible alarms, acquires weather sensor data, manages data exchange with the local control centre, from which it receives all commands. The infrared sensor data processing is based upon the following procedure: The infrared sensor measures the radiation flow coming from a small angular region, such as 1 degree x 1 degree; the vertical coverage of the sensor is 15 to 20 degrees and is obtained by means of a linear array of sensitive elements. All data coming from a detector is taken into account: in our case taken as an example, there are 360 datum points, one per azimuth degree covered. The number of data may be less if the area to be monitored is only part of a whole round angle.
The processor calculates the value of the derivative of the signal. This provides for the elimination of the signal long term changing effects, on an angle scale of 10 degrees for instance.
Such variations are typically due to the variation of the angle between the line of sight of the sensor and the position of the sun.
On the contrary, point variations are left unchanged, when less or equal to 1 degree, as these are typical signals of fires developing. The processor then extracts the mean square value of the fluctuations of the signal subject to derivation for each group of data corresponding to a vertical position which we shall call line.
Such value is proportional to the fluctuations of the background on the line itself and, multiplied by a suitable constant value, it is taken as a threshold for the detection of possible signals.
Based upon the threshold determined above, the processor identifies any signal present above such threshold on a line basis. The azimuth angle of the signal is compared with that of signals detected in the previous scans. This is necessary to confer a better reliability to the alarm through a number of consecutive confirmed appearances.
In operation, an alarm is taken as true and therefore transmitted to the local control centre only if it has received a number of confirmations greater than or equal to two in four successive scans.
It is to be noted that this procedure may be completed by the peripheral detection unit in about three minutes, therefore reducing the present detection times of a fire in wooded areas quite considerably.
A communications system 15, such as a radio link remotely controlled by the processor, provides for digital transmission of detected alarms detected by the IR sensor, of weather data and of the TV image to the local control centre.
At the local control centre, the transmitted data is sent to units which perform their processing, registration and integration with data available in cartographic, thematic and historical archives. The local control centre consists of the following:
A TV monitor 6 and a video recorder 7 for the viewing and possible recording of the TV images coming from the remote detection centres.
One or more processors with the following functions:

A: Control of the peripheral stations, exchange of commands and data.
B: Visualization of alarms, notified by the peripheral detection stations, on topographic maps of the area by means of three dimensional projection; calculation of possible intersections between alarms coming from different peripheral stations so as to assure an even more accurate location.
C: Integration of alarms with instantaneous weather data, with data banks containing information on the distribution of vegetation, on recent weather conditions and on human presence in the area.
D: Following integration of data and as a function of it, a fire propagation model is developed; such model is described later on in detail and it is one of the most innovative points of this invention.
E: Recording of data on hard disc or on peripheric units 8 such as tape recorders or optical discs.
F: System status display including possible alarm messages on printer 9.

We shall now describe briefly the procedure adopted for the forecast of the evolution of the observed fire.
The function provided by the program may be performed during operation of the fire fighting system (called in the following on line functions) or separately (off line). The main functions performed by the program are the following:
Digitising of topographic and thematic maps. The data which is available from this digitising are the substrate absolutely necessary for the visualization of alarms on the monitor display of the processor and for the development of the forecast algorithms of the fire development.
Peripheral management: This function preferably used off line transports onto paper the graphics displayed on the monitor; this is the documentation required by the fire fighting squads.
Intervisibility management which is performed between any point of the map and one of the peripheral detection stations. This function is used mostly during setting up of the system and it guides in the selection of the best sighting of the peripheral detectors.
Forecast of the fire development. The model is based upon the speed and direction of the wind, on ground gradient and type of fuel, resulting in a propagation speed of the fire as a function of absolute azimuth against north. The algorithm adopted utilises the following parameters:

Vfo = Intrinsic average speed of propagation of the fire.
Vfc = Variation of the fire propagation speed depending upon the type and humidity of the burning vegetation. Data on the distribution of vegetation is each time read from the data bank.

The effect of wind is quantified by the following parameters which have an effect on the propagation speed:

Ci = increment constant due to the greater oxygenation due to wind. It is independent of angle with wind direction, but depends on its intensity.
Ct = transport constant of the fire front edge, which depends upon the angle between the propagation line and wind direction.

The program provides a graphic output overlayed on the digitised topographic map showing the successive positions of the fire front edge at pre established time intervals.
Now we shall proceed with the detailed description of system operation, with illustrative non limiting purposes, making reference to the two figures mentioned above.
At the peripheral detection site (Figure 2), the data which is detected by the infrared sensor 10 are acquired and processed by local processor 13. One of the tasks of the processor is also the management of rotating platform 12 onto which the IR sensor and the TV camera 11 are fitted. Following interrogation of weather station 14, the processor transmits the position of any possible fire together with weather data by means of the communications system 15. The TV camera transmits images directly to the local control centre by means of the communications system.
The data coming from the peripheric detection station 1 is sorted by the communications subsystem 2. The TV video is visualized on monitor 6 and can also be recorded 7. The infrared sensor data regarding the position of any alarm is fed to processor 3 which places them on the topographic maps. The modelling program 4 develops a forecast of the fire evolution in the hours following detections, relying upon historic, weather, vegetation and other data contained in data bank 5. The weather data acquired in the last scan are inserted in the data bank.
All alarms are processed on the system monitor, on printer 9 and possibly recorded on mass memory 8.

Claims

Fire fighting system, mainly intend for the safeguard of wooded areas, for raising a fire alarm comprising a peripheral detection station (1) including:
- an infrared sensor (10) for detecting a given surveyed area, which infrared sensor measures the radiation flow coming from a small angular region of said area,

- rotating means (12) supporting the infrared sensor (10), which confers an azimuth scan to the infrared sensor,

- a local processor (13) which acquires data from the infrared sensor (10) and manages data exchange with a local control centre, from which it receives commands,

- a peripheral station communications subsystem (15) provides for transmission of data to the local control centre;
and said local control center including:
- a communications subsystem (2) which receives the data sent by said peripheral station communications subsystem (15) and emits said commands for controlling of the local processor (13),

- a peripheral memory unit (8) for recording of data,

- a central processor (3) which controls the peripheral detection station (1), controls the exchange of commands and data, illustrates the notified alarm on topographic maps of the area, records data on said peripheral memory unit (8), displays system status and integrates the notified alarm with data of a historical data bank (5) containing information on the distribution of vegetation of the surveyed area;
characterised in that the local processor (13) of the peripheral detection station further acquires data from means for collecting current weather data (14) included in the peripheral detection station (1), provides for extraction of fire alarm and causes the transmission of the alarm signal and the weather data to the local control centre via the communications subsystems (15, 2), and in that the central processor (3) of the local control centre further integrates the alarm extracted by said peripheral detection station (1) with instantaneous weather data and with data of the historical data bank (5) further containing information on recent weather conditions, as to develop a fire propagation model as a function of said integration, whereby the model is based upon the instantaneous weather data, the vegetation distribution, and the recent weather conditions, resulting in a propagation speed and direction of the fire.
Fire fighting system as claimed in claim 1, characterised in that the means for collecting current weather data comprises a group of weather sensors (14) which provide for data on temperature, relative humidity, pressure, wind speed and direction, solar radiation and rain rate.
Fire fighting system as claimed in claim 1 or 2, characterised in that the historical data bank (5) further contains information on the ground gradient and on human presence in the surveyed area, which information are used for the calculation of the fire propagation model and for the display of area to be protect particularly respectively.
Fire fighting system as claimed in any of claims 1 to 3, characterised in that the peripheral detection station (1) further comprises a TV camera (11) for possible visual monitoring of said surveyed area, fitted onto the rotating means (12), and in that the local control center further comprises a TV monitor (6) for viewing of the TV images taken from the TV camera (11) of the peripheral detection station (1) and transferred with the aid of said communication subsystems (15, 2), and a video recorder (7) for possible recording of the TV images.
Fire fighting system as claimed in any of claims 1 to 4, characterised in that the local control centre further comprises a printer (9) on which alarm messages generated by the central processor (3) are printed.
Fire fighting system as claimed in any of claims 1 to 5, characterised in that the infrared sensor (10) has a spectral sensitivity such as to provide an optimum detection of hot sources within 300-700°C against an ambient temperature background within 0-40°C.
Fire fighting system as claimed in any of claims 1 to 6, characterised in that the rotating means is a rotating platform (12) managed by the local processor (13) of the peripheral detection station (1), which confers an azimuth scan to the infrared sensor (10) and the TV camera (11), in case it is available, over 360 degrees.
Fire fighting system as claimed in any of claims 1 to 7, characterised in that the signal emitted by the infrared sensor (10) reaches the local processor (13), which calculates the value of the derivative of said signal and extracts the mean square value of the fluctuations of the signal subject to derivation for each group of data corresponding to a vertical position, multiplies such mean square value with a constant value and supplies a threshold value for the detection of possible alarm signal.
Fire fighting system as claimed in any of claims 1 to 8, characterised in that the local control centre controls a plurality of peripheral detection stations (1).
Fire fighting system as claimed in claim 9, characterised in that the central processor (3) receives the alarms coming from different peripheral detection stations (1) and calculates possible intersections between said alarms so as to assure an even more accurate location of the fire.